Field of the Invention
The present invention relates to a calibration method for an encoder, a measurement apparatus using an encoder, an exposure apparatus, and a method of manufacturing an article.
Description of the Related Art
An exposure apparatus for forming a pattern on a substrate is required to accurately position a stage for holding a substrate. To achieve this, it is important to accurately measure the position of the stage. An exposure apparatus may use an encoder to measure the position of a stage, as described in Japanese Patent Laid-Open No. 2007-129194. The encoder includes a scale, and a light receiving unit which radiates the surface of the scale with light and receives reflected light, and can detect the relative position between the scale and the light receiving unit.
However, if the surface of the scale deforms, the deformation causes detection errors in the encoder, thereby making it difficult to accurately position the stage. To solve this problem, Japanese Patent Laid-Open Nos. 2007-004175 and 2008-112160 propose a method in which an exposure apparatus using an encoder forms a pattern on an evaluation substrate, and calibrates the encoder based on the pattern formed on the evaluation substrate.
A scale may have partially deformed. In this case, calibrating the scale over the entire surface of the scale means that calibration is performed in a portion of the scale where no detection errors of the encoder occur, thereby decreasing the efficiency.